1. Field of the Invention
The present invention relates to an organic electroluminescence (OEL) device and a manufacturing method thereof. More particularly, the present invention relates to an organic electroluminescent device having an excellent luminous efficiency, long service life and high brightness, and a manufacturing method thereof.
2. Description of the Related Art
In recent years, computer, communication and consumer (3C) products have become the major trend of high technology. More particularly, the portable electronic devices are also the essential products of development. Essentially, a display device is required in all of the products. To date, the display may be classified into an organic electroluminescent display (OELD), a plasma display panel (PDP), a liquid crystal display (LCD), a light emitting diode display, a vacuum fluorescent display, a field emission display (FED) and an electro-chromic display. Among the above mentioned displays, the organic electroluminescent display, has the advantages of self-luminance, no view angle dependence, low power consumption, simple manufacturing process, low cost, low operation temperature range, high response speed and high full color resolution etc. Therefore, the organic electroluminescent display has huge potential applications and has become the main trend for the next generation displays.
The organic electroluminescent device performs display by using the self-luminescent property of the organic luminescent material. The structure of the organic electroluminescent device includes at least two electrodes and an emitting layer (EMT) between the electrodes. When a current is applied via the diode and the cathode, electron holes from the anode and electrons form the cathode are combined in the emitting layer, and excitons are generated, therefore, lights having a variety of colors can be generated by using a variety of materials having different properties. The above description describes the emitting principle of electroluminescence. In order to improve the luminous efficiency of the organic electroluminescent device, the organic luminescent layer may be formed from the small molecules of the organic electroluminescence by the vacuum evaporation method. A structure of a conventional organic electroluminescent device is described in the following.
FIG. 1 is a cross-sectional view schematically illustrating a conventional organic electroluminescent device. Referring to FIG. 1, a conventional electroluminescent device 100 includes a substrate 110, an anode 120 formed on the substrate 110, a emitting layer 130 formed on the anode 120, and a cathode 140 formed on the emitting layer 130. Moreover, a cover 160 is formed on the cathode 140 for covering and packaging the organic electroluminescent device 100.
In order to emit a white light from the conventional organic electroluminescent device 100, the emitting layer 130 is generally constructed by a blue emitting layer 132 and a reddish orange emitting layer 134. Therefore, a white light is generated by the blue light and reddish orange light that are complementary color. However, because the service life of the conventional blue emitting material is short, i.e., the decay of the blue light emitting material is faster than that of the reddish orange emitting material. Therefore, when the blue emitting layer 132 starts to decay, the white light emitted from the organic electroluminescent device 100 will have chromatic aberration.